Hydrodesulfurization of residua

ABSTRACT

A process for the hydrodesulfurization of residua. A residuum is contacted with a high activity maintenance catalyst comprising an oxide or sulfide of cobalt or nickel and an oxide or sulfide of molybdenum or tungsten deposited on a silica-stabilized alumina support, having a maximum of its surface area in pores having 30 to 80 A diameters. A preferred catalyst is characterized as one having at least 180 M2/g. of surface area in pores with diameters ranging from 30 to 80 A, and less than 0.25 cc./g. of the pore volume in pores having a diameter greater than 100 A.

United States Patent [191 Adams et al.

[ 1 *Nov. 6, 1973 HYDRODESULFURIZATION OF RESIDUA [75] Inventors: ClarkE. Adams, Baton Rouge, La.;

William T. House, Seabrook, Tex.

[73] Assignee: Esso Research and Engineering Company, Linden, NJ.

[ Notice: The portion of the term of this patent subsequent to Apr. 28,1987, has been disclaimed.

[22] Filed: Mar. 20, 1972 21 Appl. No.: 236,383

Related US. Application Data [63] Continuation-in-part of Ser. Nos.648,604, June 26, l967, Pat. No. 3,509,044, and Ser. No. 20,847, March18, 1970, abandoned.

Primary ExaminerDelbert E. Gantz Assistant ExaminerG. J. CrasanakisAttorney-Leon Chasan et al.

[5 7] ABSTRACT A process for the hydrodesulfurization of residua. Aresiduum is contacted with a high activity maintenance catalystcomprising an oxide or sulfide of cobalt or nickel and an oxide orsulfide of molybdenum or tungsten deposited on a silica-stabilizedalumina support,

[52] US. Cl. 208/216, 252/455 R 51 Int. Cl C10g 23/02 havmg a maxmum ofSurface area Pores havmg {58] Field of Search 208/216 A diameters- APreferred catalyst is character ized as one having at least 180 M /g. ofsurface area in [56] References Cited pores with diameters ranging from30 to 80 A, and less than 0.25 cc./g. of the pore volume in pores havinga UNITED STATES PATENTS diameter greater than A. 3,169,918 2/1965 Gleim208/216 3,340,180 9/1967 Beuther et a1. 208/216 13 Claims, 3 DrawingFigures 1 I I I I I I I I I I I I I I g V a: Z I 2 3 e Z N o In 4 o I II I l I I I I I I I o o o o o o o O O O O O O O O N (O I!) q 10 uPATENTEUxuv s 1973 SHEET 10F 3 lllll FIGURE PATENTEDNDV s 1975 SHEET 2OF 3 Ill] All/\LLOV NOILVZIHFH'IHSSOOUGXH FIGURE 2 1HYDRODESULFURIZATION OF RESIDUA BACKGROUND OF THE INVENTION Thisapplication is a continuation-in-part of our applications Ser. No.648,604, filed June 26, 1967 (now US. Pat. No. 3,509,044) and Ser. No.20,847, filed Mar. 18, 1970, now abandoned.

FIELD OF THE INVENTION This invention relates to a process for thehydrodesulfurization of a hydrocarbon residuum feed, especially apetroleum residua. More particularly, the invention relates to thehydrodesulfurization of a petroleum residuum in the presence of acatalyst having a maximum of its surface are in pores having 30 -'80 Adiameter. A preferred catalyst is characterized as one having at least180 M /g. of surface area in pores with diameters ranging from 30 80 A,and less than 0.25 cc./g. of the pore volume in pores having a diametergreater than 100 A.

DESCRIPTION OF THE PRIOR ART The process of the invention is applied toa hydrocarbon residuum feed, especially a petroleum residuum feedstock.The three majorcharacteristics of residua other than molecular weightwhich distinguish them from distillates are that residua contain (1asphaltenes and other high molecular weight aromatic structures whichseverely inhibit the rate .of hydrodesulfurization, and cause catalystdeactivation, (2) ash forming constituents such as metallo-organiccompounds which result in catalyst contamination and interfere withcatalyst regeneration, and (3) a relatively large quantity of sulfurwhich gives rise to objectionable quantities of S and S0 upon combustionin industrial furnaces.

Hydrodesulfurization has long been recognized as a means of removingsulfur from residual oils and asphalts. In addition to sulfur removal,hydrodesulfurization processes generally result in improvement in otherproperties of residual fuels by nitrogen removal and metals removal. Inspite of these benefits, the commercial application ofhydrodesulfurization to residua to produce improved residua fuels hasbeen minimal, due to low economic incentives for improved fuel oilproperties and high operating costs associated with the relatively highpressure required. The hydrogen consumption and short catalyst life havealso hindered the utilization of such processes.

The principal object of the present invention is to reduce the sulfurcontent of a hydrocarbon residuum feed, especially petroleum residuawithout significantly changing the properties of the oil. The process iscentered on a generally nondestructive hydrodesulfurization process, asdistinguished from destructive hydrogenation or hydrocracking. However,some hydrocracking may take place concurrently with thehydrodesulfurization without departing from the scope of the presentinvention. Thus, conversion to gas and light ends is minimized. Anotherobject of this invention is to provide a process specifically designedto treat a feed consisting entirely of petroleum residuum asdistinguished from naphthas, gas oils or residua containing addeddiluents. In most cases satisfactory processes and catalysts have beendeveloped for the lighter materials and diluted feedstocks.

which is economically feasible in view of the low return available fromthe marketing of the treated residuum as residual fuel oil. Cost studieshave shown that the key factors are catalyst activity and catalystactivity maintenance. Therefore, the specific object of the invention isto provide a process which is carried out at moderate pressure,temperature and other conditions with a catalyst which features low costand high activity maintenance. Further objects and advantages of theinvention will be apparent from the following description whichdiscloses certain nonlimiting embodiments.

SUMMARY OF THE INVENTION The objects of the present invention areattained by hydrodesulfurizing hydrocarbon residua, especially petroleumresidua at moderate conditions in the presence of a catalyst comprisingan oxide or sulfide of nickel or cobalt and an oxide or sulfide ofmolybdenum or tungsten deposited upon a support material comprising fromabout 0.1 to about 6 wt. percent silica and from about 94 99.9 wt.percent alumina. A preferred catalyst is characterized as one having atleast 180 M /g. of surface area in pores with diameters ranging from 30A, and less than 0.25 cc./g. of the pore volume in pores having adiameter greater than A.

The support material can be prepared by precipitation of a hydrousalumina from a mixture containingan aqueous alkaline aluminate solution,an aluminum salt of a mineral acid, an alkali metal silicate, and acompound selected from the group consisting of aldonic acids and saltsof aldonic acids, the hydrous alumina precipitate being in the form of aslurry, filtering the slurry to increase the concentration of aluminasolids in the slurry and subsequently spray drying the slurry to form anextrudable, non-gIass-like catalyst support. More specifically, thesilica-stabilized alumina support is one having a surface area of atleast 150 M /g. and a maximum of the surface area in pores havingdiameters ranging from 30 80A. This support can be prepared byprecipitation from a mixture having a final pH of less than 9.5, atemperature ranging from 1 10 up to F., the mixture containing anaqueous alkaline aluminate solution, an aluminum salt of a mineral acid,a mineral acid, an alkali metal silicate, and a compound selected fromthe group consisting of aldonic acids and salts of aldonic acids, theprecipitate forming a slurry of hydrous alumina, filtering the slurry toincrease the concentra of alumina solids in the slurry, and subsequentlyspray drying the slurry to form an extrudable catalyst support. Thespray dried catalyst support has a bulk density of less than 0.7 g./cc.

In a preferred embodiment the pH and the temperature duringprecipitation are closely controlled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred process feedstockis a petroleum residuum obtained from distillation or other treating orseparation process. From 30 to 100 percent of the feed boils above 900F.The process is designed to treat a residuum without any pre-processing;however, when the metal content of the oil is greater than aboutSOD-1,000 ppm, it may be necessary to employ a metals removal step suchas HF treatment or solvent precipitation with propane, butane, mixturesof propane and butane, pentane, hexane or naphtha. The petroleumresiduum can be a blend of high boiling materials such as atmosphericbottoms, vacuum bottoms, deasphalted oil, visbreaker products,heatsoaked materials, gas oil cuts, and the like. The feedstocks of theinvention contain relatively large amounts of sulfur, asphaltenes,metals and ash. Some of these materials or conversion products thereofdeposit on the hydrodesulfurization catalyst when hot oil is broughtinto contact with the catalyst surface.

The feedstocks treated have the following properties and inspections:

TABLE I PROPERTIES OF PETROLEUM RESIDUA Operational Narrow Feed RangeRange Example 3 Safaniya Atmos. Resid.) Boiling above 900F. 30-10050-100 60 Gravity, API 5 to 25 10-20 15.4 Viscosity, SFS at 122F.50-5000+ 100-1000 309 Sulfur, Wt. 1-8 3-6 4.0 Nitrogen, Wt. -1 0001-050.26 Metals (ppm) Total 20-1000 80-500 127 Vanadium (pp -500 30-300 84Nickel (ppm) 5-200 10-100 32 Asphaltenes, Wt. l-20 2-10 7.2 Pour, F.0-200 25-100 45 The composition and characteristics of the support aremost important aspects of the invention. The alumina support of thepresent invention is stabilized with silica. Hydrodesulfurizationcatalyst supports containing silica have been suggested in the past.However, silica was included in the support when the feedstock wasgasoline or light gas oil or when a significant amount of hydrocrackingwas desired. It was felt that the presence of any significant amount ofsilica in the hydrodesulfurization of residuum would cause significantcracking with consequent coke make and catalyst fouling. Thus, it wasentirely unexpected that relative catalyst activity could be greatlyimproved by the presence of a relatively small quantity of silica in thecatalyst support, i.e., as little as about 0.1 wt. percent, preferablyfrom about 0.5 to about 6 wt. percent.

The support can be prepared by precipitating the oxides or hydratedoxides of aluminum and silicon from aqueous solutions of water salts ofthese metals. For example, suitably proportions of the water solublesalts of aluminum such as the sulfate, chloride or nitrate and suitableproportions of water soluble silicon salts such as sodium silicate areprecipitated from solution by adjusting the pH of the solution withacidic or basic material. The precipitate is washed and othewise treatedto remove impurities as necessary. The support can be impregnated withthe metals while it is wet or after drying and calcining.

A preferred method of preparing the catalyst of the invention is totreat alkaline aqueous aluminate solutions which contain predeterminedamounts of silica with acidic reagents to precipitate an aluminosilicatein the hydrous form. A slurry produced by this technique is then driedby known methods to furnish a preferred catalyst support of thisinvention. The supports of the types prepared above are then imregenatedwith metals which promote a hydrodesulfurization reaction.

The preferred alkaline aqueous aluminate solution is a solution ofsodium aluminate. It is understood that other alkali metal aluminatescan be used except they are not preferred from an economic standpoint.

The acidic reagents which can be used are the mineral acid salts ofaluminum, e.g., aluminum halides, nitrates, and sulfates. Also usefulare the well-known mineral acids themselves, e.g., hydrochloric nitric,sulfuric acids, and the like.

The conditions for preparing the support are so controlled that thefinished support has an apparent bulk density of less than 0.70 g./cc.It is further characterized as being opaque as distinguished from glassyin appearance (indicating that a large quantity of the alumina is in acrystaline form). The catalyst is extrudable.

In preparing these preferred catalytic materials, the following tablecontains a summary of the preferred conditions.

TABLE II Operational Preferred Conditions Range Range 1. Concentrationof starting 1.2-5% 1.2-1.7% aluminate solution, expressed as A1 0 ll.Precipitation Temperature -120F. 1 10-l20F. Ill. pH 5-9.5 6-9 IV.Reaction Time '/4-6 Hrs. /42 Hrs.

As seen above, the alumina concentration, expressed as Al O of theaqueous alkali aluminate solution must be beween 1.2 and 5.0, preferablybetween 1.2 and 3.0, the most preferred concentration being between 1.2and 1.7 percent by weight. It has been found that close control of thealumina concentration within the stated ranges is a material factor inproducing a support which can be extruded in commercial equipment.

Other important variables include pH and temperature. The precipitationmust be effected at a pH between 5 and 9.5, preferably between 6 and 9.Temperatures ranging between 105 and F., preferably 1 10 120F. must beemployed.

In the most preferred embodiment the silica-alumina support is preparedin the presence of a material selected from the group consisting of analdonic acid or an aldonate, preferably a gluconate or gluconic acid.Galactonic acid, arabonic acid, xylonic acid, manoic acid, and saltsthereof can be used as well. Suitable aldonates, salts or aldonic acids,include the sodium, potassium, zinc, magnesium, calcium and lithiumsalts of gluconic acid or other aldonic acids. This material is used inthe initial solution in amounts ranging from 0.1 6.0 wt. percent basedon the alumina content of the solution. It appears that the addition ofaldonates or aldonic acids in the preparation of the silica-alumina basehas a beneficial effect on the physical characteristics of the finalcatalyst and its effectiveness in hydrodesulfurization of residuum.

Using the general reaction conditions found in Table II, the supportresulting from the reaction is in the form of a dilute slurry. Thisslurry may then be concentrated and subjected to spray-drying operationsat temperatures ranging between 200-2,000F., preferably between200-500F. Spray-drying, particularly at the stated conditions, preservesthe base in the desired form.

Using conventional techniques known to the catalyst art, the spray-driedmaterial may be subjected to waterwashing to remove excess alkali metalions and sulfate ions. The support can then be impregnated with thecatalytic metals and extruded or pilled or otherwise formed into anydesired physical form.

The aforementioned silica-alumina hydrogels can be composited with othersynthetic and/or semi-synthetic aluminas, silica gels, and/or othersilica-alumina-clay hydrogen compositions for the purpose of adjustingthe alumina and/or silica present during impregnation. It is essentialthat the silica content of the catalyst be maintained in the range of0.1-6 wt. percent, preferably from about 0.5 6 wt. percent and morepreferably 1 to 5 wt. percent. The resulting catalyst, when calcined, ischaracterized as one havingat least 180 M /g. of surface area in poreswith diameters ranging from 30 to 80 A, and less than 0.25 cc./g. of thepore volume in pores having a dimaeter greater than 100 A.

The active metallic components in the finished catalyst are a Group VIBoxide or sulfide, specifically a molybdenum or tungsten oxide or sulfideselected from theg roup consisting of molybdenum oxide, molybdenumsulfide, tungsten oxide, tungsten sulfide, and mixtures of these and aGroup VIII oxide or sulfide, specifically a nickel or cobalt oxide orsulfide selected from the group consisting of nickel oxide, cobaltoxide, nickel sulfide and cobalt sulfide and mixtures of these.- Thepreferred active metal oxides or sulfides are nickel oxide withmolybdenum oxide and cobalt oxide with molybdenum oxide. The oxidecatalysts are preferably 'sulfided prior to use.

The final catalyst contains the following amounts of each component:

TABLE III CATALYST COMPOSITION Operational Range Preferred (Wt. Range(Wt.

Nickel or Cobalt (as oxide) 1 to 15 2 to Tungsten or Molybdenum (asoxide) 5 to 25 10 to 20 Silica 0.1 to 6 l to 5 Alumina 93.9 to 54 87 to65 The structure of the catalyst is also an important aspect of theinvention. In the hydrodesulfurization of a hydrocarbon residuum, e.g.,a petroleum residuum, a criticality of pore size has been found withrespect to activity maintenance. It has been found that pores having apore diameter in the 30-80 A range are of critical importance with heavyresidual feeds. Evidently, pores of smaller diameter than about 30 A areineffective in desulfurizing the high molecular weight molecules presentin residues and pores of larger diameter than about 80 A are rapidlydeactivated. It has been found that a maximum (greater than 50 percent)of the surface area should be present in pores having a pore diameter inthe 30-80 A range. A preferred catalyst is characterized as one havingat least 180 M /g. of surface area in pores with diameters ranging from30 to 80 A, and less than 0.25 cc./g. of the pore volume in pores havinga diameter greater than 100 A.

The pore volume distribution of a catalyst as defined by this inventionis measured by nitrogen adsorption isotherm where the volume of nitrogenadsorbed is measured at various pressures. This technique is describedin Ballou, et al., Analytical Chemistry; Vol. 32, April, 1960, pp.532-536. The pore diameter distributions for the examples of theinvention were obtained using a Model No. 4-4680 Adsorptomatmanufactured by the American Instrument Company, Silver Springs, Md. Oneskilled in the art can select catalyst manufacturing process steps andprocess conditions within the specific ranges disclosed herein toprepare catalysts having the required pore diameter, pore sizedistribution, pore volume, and surface area.

EXAMPLE 1 The following illustrates a typical catalyst preparation.

Three solutions are prepared, e.g., A, B, and C:

Ingredient Amount Solution A* Water 36 gallons Sodium Silicate Solution28% SiO, 1 13 cc.

Sodium Aluminate 23.5% A1 0 Solution 5323 cc.

48% Gluconic Acid Solution 76 cc. Solution B 98% R 80, 850 cc. into 4.5

gallons water Solution C 9.5% Alum Solution 3.3 gallons *Total A1 0 insolution 1.3%.

Solution B is added to Solution A over a period of 23 minutes. At thispoint the temperature of the reaction mixture is 118F.

Solution C'is then added to the mineral acid solution over a 19-minuteperiod. The tempeature during addition remains at 1 18F. The final pH,after the above additions, is 8.8. The slurry was filtered, reslurried,spray dried, washed to remove soluble salts, and redried.

The finished silica-alumina support has a pore volume of 2.36 cc./g., asurface area of 310 M /g., and an apparent bulk density of 0.18 g./c

EXAMPLE 2 A silica-alumina support is prepared in the manner set forthin Example 1 and is composited with suitable quantities of molybdenumoxide and cobalt carbonate by hydrothermal impregnation; The slurry isfiltered and dried to provide a catalyst (dry weight basis containing3.5 percent cobalt oxide, 12.0 percent molybdenum oxide, 1.7 SiO and thebalance alumina). This catalyst is hereinafter referred to as CatalystB. The support can be impregnated with the other hydrogenation metals ofthe invention, i.e., nickel and tungsten in the same manner.

A commercial catalyst was selected for the purpose of obtainingcomparative data. It contained 3.5 weight percent cobalt oxide, 12.5weight percent molybdenum oxide, 0.2 weight SiO and the balance alumina.This catalyst is designated hereinafter as Catalyst A.

The hydrodesulfurization reaction is carried out in a conventionalreactor of the fixed bed, moving bed, or fluidized bed type. In additionto these reactor types, it has been found that the catalyst of thepresent invention is also extremely useful when used in a slurry orebullient bed. Considering the nature of the feedstock, the reactionconditions are relatively mild. The oil is contacted in'the liquidphase. Typical conditions for the hydrodesulfurization are as follows:

TABLE IV REACTION CONDITIONS Operational Preferred Range RangeTemperature, F. 500825 650-800 Pressure, Psig. 200-2500 5001800 SpaceVelocity, V/V/I-Ir. 0.01-5.0 0.12.0 Hydrogen Rate, SCF/Bbl. 300-10,00010004500 With these conditions, viscosity reduction of the oil due toprocessing is not excessive and fuel oil viscosities which meetspecifications are easily obtained.

The following comparative examples and tables demonstrate theimprovements in hydrodesulfurization of residuum which can be obtainedwith the catalysts of the invention as compared to a group of prior artcatalysts.

EXAMPLE 3 A pilot plant unit containing 200 cc. of catalyst was used inthis example. The oil was passed down through the catalyst bed.

The catalyst was calcined overnight at 1,200F. and then sulfided using 5wt. percent carbon disulfide in a light petroleum distillate. Sulfidingwas carried out at l V/V/l-lr., 1,500 psig, and 1,500 SCF/B hydrogenrate. The reactor was held at 500F. for 2 hours and then raised to 750F.and held there for 16 hours. The temperature was lowered to near 700F.and feed was cut EXAMPLE 4 Table V shows the relative activity of anumber of hydrode sulfurization catalysts. All runs were carried out onSafaniya atmospheric residuum (4.0% S) at the following conditions:1,500 psig, 725F., 3,000 SCF H lBbL, l V/V/Hr., 60 cc. catalyst.

TABLE V Composition (alumina plus the Rel. vol. act. for day followingmaterials) Bulk Catalyst (wt. percent) density 1 7 14 21 A 3.5 C00, 12.5MoO ,0.2 810;... 0.66 *100 58 43 36 B... 3.5 CoO, 12.0 MoO ,1.7 SiOz0.65 180 140 115 110 C 4.0 NiO, 15.0 M003, 3.4 SiOz 0.65 150 115 100 90D 10.0 C00, 20.0 M00 3.9 $10 1.0 160 113 105 100 E 10 N10, 20.0 M00 3.9SiO 0.88 160 113 105 F... 7.0 NiO, 23.0 W03, 3.9 SiOz 0.88 94 70 63 60G... 3.5 CoO,12.5 MoO ,6.0 SiO 0.59 280 105 65 50 H 3.5 CoO,12.5 M00 8.6SiO 0.57 280 80 50 1... 6.0 NiO, 13.0 MoO3,14.0 SiO 0.54 160 45 J4.0NiO,15.0 MoO ,0.3 SiO 0.59 70 40 Equivalentto 67% desulfurization rliw t. 17 S in product with 4.0 wt. S in feed.

in. The feedstock was s Safaniya residuum having the properties setforth in Table l. Side-by-side comparative runs were made to give adirect comparison to measure the activity decline of the catalyst. Thepressure was 1,500 psig., the space velocity was 1 V/V/Hr., and thehydrogen rate was 1,500 SCF/Bbl. The reactor temperature was increasedas necessary to obtain 55 percent desulfurization of the residuum.

Catalyst A was select for comparison because it was effective inhydrodesulfurization of distillate stocks. It contained 3.5 wt. C00 and12.5 wt. M00 on a support containing 0.2 wt. SiO and the balancealumina. Catalyst B is prepared in a manner set forth earlier in thisspecification. FIG. 1 sets forth the temperature increase requirement(TIR) for runs with Catalyst A and Catalyst B. The TIR for Catalyst B is0.l7F./day, showing a very low activity decline. Catalyst A exhibitedthe usual initial high activity decline, then lined out at a TIR of1.7F.lday. Thus Catalyst B has an activity maintenance 10 times betterthan that of Catalyst A. This, result was completely unexpected becausethe two catalysts demonstrated no such difference in thehydrodesulfurization of distillates.

Runs with Catalyst B demonstrate the following improvements: (I) greatlyimproved catalyst life, (2) lower pressure operation (1,500 vs. 2,200psig, which was previously considered necessary for good catalyst life),and (3) lower gas rates (1,500 vs. 3,000 SCF/Bbl. also previouslyconsidered necessary for good catalyst life). In addition, the newcatalyst shows about half the metals laydown usually experienced withpetroleum residuum feeds. These improvements make residuumhydrodesulfurization by our process attractive from a cost standpoint.

Kuwait atmospheric residuum 3.8 wt. %,S) was desulfurized over CatalystsA and B at 800 psig, l

The relative volume activity of the catalysts employed in the process ofthe invention, i.e., catalysts B, C, D, E, F, and G is far superior tothe activity of the prior art catalysts, i.e., A, H, I and J. Theresults reveal the criticality of silica in the range of about 0.5 to 6wt. percent in the catalyst base in attaining high activity and activitymaintenance. Since catalysts are sold by the pound, we' prefer thecatalysts having the lowest metals content and bulk density which willgive superior activity maintenance, i.e., catalysts like Catalyst B.

The catalysts employed in the process of the invention have excellentsurface area stability and they are effectively regenerated byconventional techniques at temperatures ranging from 600l ,000F.

EXAMPLE 5 Catalysts A and B of the first two examples have some similarproperties as shown by lines one to five of Table VI, below. Forexample, the overall surface areas are nearly equivalent. However, thenature of the surface areas are considerably different. Catalyst A has asurface area in 30 to A diameter pores of 86 square meters per gram.Catalyst B has a surface area in 30 to 70 A diameter pores of 174 squaremeters per gram. The relatively large surface area in the pores in the30 to 70 A diameter range of Catalyst B seems to be one of the reasonsfor its extended-life in processing residua.

TABLE VI Cat. A. Cat. B. Cat. E Surface Area, M lg. 253 266 271 PoreVolume, ccJg. 0.58 0.50 0.24 Bulk Density, g./cc. 0.63 0.71 0.88 PelletDensity, g./cc. 1.10 1.20 Pellet Strength 1 1.0 16.5 0.2 2.0 3.9

CaMoO,, Wt. (by X-ray) 2 O Surface Area in 30-70 A. Pores,

Mlg. 86 174 136 Relative Wt. Activity at Day 21 36 91 67 After 21 daysof operation at the conditions set forth in Examples 4 and 5, Catalyst Bhad a weight activity of 91 compared to a weight activity of only 36 forCatalyst A. Weight activity is determined by Relative Vol. Activity X(Bulk Density of Reference Catalyst/Bulk Density of Test Catalyst) In aseries of comparative runs, Catalyst B proved to have at least fivetimes as much catalyst life as Catalyst A. Similarly, Catalysts C and Ewhich are nickelmolybdenum type catalysts had a high relative weightactivity. Thus, a surface area in 30 to 70 A diameter pores of at least100 M /g, preferably 100-300 M /g., provides excellent activity andactivity maintenance. It had been previously thought by the inventorsthat the critical pore size range was 30-70 A in diameter (US. Pat. No.3,509,044); however, it is now believed by the present inventors thatthis range extends from 30-80 A in diameter. A preferred catalyst is onehaving at least 180 M /g. of surface area in pores of diameters ranging30 to 80 A, and less than 0.25 cc./g.- of the pore volume in poreshaving a diameter greater than 100 A.

ing (a) large surface area 314 M /g.; (b) small pore volume inmacropores, i.e'., in pores with diameters greater than 100 A; and (c) alarge surface area in pores with diameters ranging between to 80 A (235M /gram). The hydrogenation component comprises 3.5 weight percentcobalt oxide and 12.5 weight percent molybdenum oxide; the catalyst alsocontains 1.8

wt. SiO v Catalyst L, a prior art catalyst, also described in detail inTables VII and VIII, is similar in composition to Catalyst K, having arelatively high surface area, i.e., 302 Mlg. Pore volume in pores withdiameters greater than 100 A is also low. However, as shown by referenceto Table VIII, Catalyst L has almost 40 percent of its surface area inpores having diameters below 30 A. Moreover, the surface area in poreshaving diameters between 30 and 80 A is relatively low, i.e., 176 M /g.

Catalyst M is similar in composition to Catalyst K, also having arelatively high surface area. In Catalyst M, however, it will beobserved that the surface area in pores having diameters greater than 80A, as well as pore volume in pores with diameters greater than 100 A, asobserved by specific reference to Table VIII, are high in comparison tocatalyst K, the catalyst of this invention.

TABLE VIl.SPEClFIC INSPECTION OF CATALYST PORE SIZE DISTRIBUTIONS detailby reference to Tables VII AND VIII, is one hav;

Catalyst K Catalyst L Catalyst M Pore Surface Pore Surface Pore SurfaceDiameter A volume area volume area volume area 600-500 0.5 0.0 0.5 0.03.9 0.6 500-400.... 0.8 0.1 0.8 0.0 5.0 1.0 400-300.. 1.4 0.2 1.3 0.16.2 1.6 300-200.. 3.2 0.8 2.5 0.4 7.2 2.6 200-180.. 1.2 0.4 0.8 0.1 2.21.0 180-160.. 1.6 0.6 1.0 0.2 2.7 1.4 160-140.. 2.5 1.0 1.2 0.3 3.4 2.1140-120.. 4.2 2.0 1.6 0.5 5.2 3.6 120-100.. 7.2 4.2 2.3 0.9 8.4 7.0100-90.... 5.4 3.6 1.6 0.7 6.1 5.8 90-80..... 7.7 5.8 2.3 1.1 8.4 8.980-70... 9.6 8.4 3.7 2.0 9.9 12.0 70-60.... 12.5 12.3 6.2 3.9 10.8 15.160-50..... 13.9 16.1 10.2 7.7 10.5 17.4 -40.... 14.6 20.7 17.6 16.4 9.419.1 40-30.... 12.6 23.0 23.5 28.2 0.0 0.0 30-20..... 0.0 0.0 22.2 36(6)8(0 8.8 20-14 0.0 0.0 0.0 0. Pore v 1. in pores less than 600 Ml./g 0.490.29 0.67 Surface Area, M lg, 314 302 313 The following comparative datawere selected'to il- TABLE VIII lustrate the superior activity of thecatalysts of this in- CATALYST INSPECTIONS vention which have a majorityof the surface area in 50 Catal st K L M pores haVingdiameters rangingbetween 30 to 80 A as peedgock TJM TJM contrasted with prior artcatalysts of different pore size Composition, wt distributions. In theseries of hydrodesulfurization runs 35 specifically described byreference to Exarnple 6, i 3 125 l [27 mediately following, a catalyst Kcharacterized as hav- SiO, 1 P 1.8 0.8 4.0 ing at least 180 M /g. ofsurface area in pores with di- 'gg azg 314 302 313 ameters ranging from30 to 80 A and less than 0.25 Total Pore Volume, cc/ of its ore volumein ores of diameter reater ML/G 050 P p g Avg. Pore Diameter, A. 63.746.4 99.7 than 100 A, is compared with prior art catalysts L and BulkDensity, G/ML 0.70 0.82 0.52 M of different, and more random pore sizedistribution, gi g g 22? 32 the runs being conducted at similaroperating condip volume in p ti with Diameters Greater than 100 A., ML/G0.12 0.10 0.41

Area in Pores EXAMPLE 6 Surface with Diameters Catalyst was prepared toprovide a silica-alumina gffi A" catalyst as in the preferred practiceof this invention. C M/G 23]?I 17(6) 193 Q atal st This catalyst, theproperties of which are described in peedgock SAF SAF TJM Composition,Wt.

C 3.5 3.5 3.6 MG 10.0 M00, 12.0 20.0 12.5 20.5 1.7 3.9 0.2 PhysicalProperties Surface Area, M /g. 260 271 224 182 Total Pore Volume,

ML/G 0.49 0.26 0.58 0.51 Avg. Pore Diameter, A. 75.4 38.4 103.6 1 12.1Bulk Density, G/ML 0.68 0.88 0.66 0.55 Catalyst Form 14x65 14x65 14x6514X65 As Tested Mesh Mesh Mesh Mesh Pore Volume in Pores with DiametersGreater than 100 A., ML/G 0.15 0.02 0.33 0.30 Surface Area in Pores withDiameters between 30 A. and 80 A., Sq.

M/G 190 147 l 17 81 'TiaJuana Medium Atmos. Btms.; 15.2AP1 gravity;2.13% sulfur; 277 ppm vanadium; 33.5 ppm nickel.

Safaniya Atmos. Btms.; 15.4AP1 gravity; 4.0% sulfur; 84 ppm vanadium; 32ppm nickel.

A Tia Juana Medium (TIM) atmospheric residuum described by reference toTable VIII was desulfurized,

in the presence of hydrogen, by passage over catalysts, K, L and M,respectively, and the activities of the cata- EXAMPLE 7 To furtherillustrate the novelty of the catalysts of this invention, Catalysts N,O, P and Q were prepared, these catalysts having the properties shown inTable VIII, supra. In addition, the percentage of surface area in poresof varying diameter, as well as percent of pore volume in these poresizes, are listed in Table IX.

Of these catalysts, Catalyst N was prepared to meet the specificationsrequired of the catalyst of the present invention. By reference to TableIX it will be observed that Catalyst 0 has 73.2 percent of its TABLEIX.CATALYST PORE SIZE DISTRIBUTION Catalyst N Catalyst 0 Catalyst PCatalyst Q Pore Surface Pore Surface Pore Surface Pore Surface DiameterA volume area volume area volume area volume area 600-500 1.0 0.1 0.40.0 1.0 0.2 1.7 0.3 500-400.... 1.6 0.2 0.4 0.0 1.7 0.3 3.1 0.8400-300.... 2.6 0.5 0.6 0.1 2.9 0.8 6.1 1.9 300-200.... 5.1 1.5 0.9 0.17.3 2.7 18.3 9.3 200-180.... 1.7 0.6 0.2 0.0 2.5 1.2 4.8 2.8 180-160....2.2 0.9 0.3 0.1 4.1 2.2 6.1 4.0 160-140.... 3.2 1.6 0.4 0.1 6.5 3.9 9.06.7 140-120.... 5.0 2.8 0.9 0.3 9.0 6.3 6.9 6.0 120-100. 8.3 5.6 1.7 0.612.4 10.3 12.7 13.2 100-90... 6.0 4.6 1.3 0.5 9.8 9.3 5.2 6.1 90-80....8.4 7.3 3.1 1.4 10.1 10.7 3.6 4.7 80-70.... 10.7 10.5 4.5 2.3 9.3 11.24.7 7.0 70-60.... 12.6 14.3 6.9 4.0 8.5 11.7 7.3 12.6 60-50.... 13.117.6 11.4 7.8 6.5 10.7 4.9 9.9 50-40.... 12.3 20.2 17.3 14.7 4.7 9.5 5.112.7 -30.... 5.3 10.6 23.4 25.5 3.7 9.3 0.7 2.0 30-20. 0.0 0.0 22.6 34.90.0 0.0 0.0 0.0 20-14. 0.0 0.0 3.8 7.6 0.0 0.0 0.0 0.0 Pore v 600 0.490.25 0.47 0.51 Surface Area, Sq. M/G 260 271 224 182 lysts compared. Ineach of the runs, the catalyst sulfidsurface area in pores havingdiameters ranging being was carried out as described in Example 3. Atthe end of the sulfiding period, the temperature was lwoered to 725F.and feed was cut in. The runs were conducted at 1,500 psig, a spacevelocity of 1 V/V/I-Ir., and a hydrogen rate of 3,000 SCF/Bbl. As thehydrodesulfurization runs progressed, the amount of desulfurizationgradually decreased from day-to-day. The relative hydrodesulfurizationactivity of each of individual Catalysts K, L and M, calculated for theTJM' feed from Second Order kinetics in sulfur removal from petroleumresidua according to scale calculated by 100 X (observed rate constantstandard rate constant), is graphically described for a 21-day period byreference to FIG. 2.

The activity plots for these catalysts clearly demonstrate the crucialnature of the dual requirement relat'ive to the amount of surface areaexisting in pores having diameters ranging between 30 to 80 A and lessthan tween 30 to A. Total surface areas were somewhat reduced in thisseries of experiments as a result of calcination of Catalysts N, O andP, at a temperature of 1,2- 00F. However, this only serves to furtherillustrate the importance of surface area concentration within a certainpore size range, as compared with just a so-called large surface area.

In addition, Catalyst 0 was prepared in a manner designed to essentiallyduplicate a prior art. catalyst (that disclosed in US. Pat. No.3,340,180 to Beuther et al.).

A series of runs was conducted as described by reference to Example 6except that a Safaniya atmospheric residuum was used as a feed, and theruns were conducted at 700F. Comparison of the hydrodesulfurizationactivities of these catalysts were made, the results being graphicallydescribed by reference to FIG. 3. It is thus clearly shown that bothCatalysts O and P are significantly less active than Catalyst N.Catalyst 0 is less active than Catalyst N, even though the total'surface area of Catalyst is higher than that of Catalyst N. Reductionin activity is found directly attributable to Catalyst 0 having a lowersurface area in pores having diameters in the range 30 to 80 A which isillustrated by the fact that the percent surface area in pores havingdiameters less than 30 A is 42.5 percent.

Catalyst P is illustrative of the effect of low surface area inporeshaving diameters in the 30 to 80 A range and high pore volume inpores with diameters greater than 100 A. This catalyst, it will beobserved, is roughly comparable to the reference-type catalyst ofCatalyst M, but having been calcined at l,200 F. as was Catalyst N, ofthe present invention.

EXAMPLE 8 To illustrate the reduced activity of a catalyst having a widedistribution of pore sizes as compared with a catalyst of thisinvention, Catalyst Q, having the characteristics described by referenceto Tables VIII and IX, was prepared and tested by desulfurizing a TiaJuana residuum feed as described, and at the conditions described, byreference to Example 6. The relative activity of this catalyst iscompared with that of Catalyst K run at similar conditions, as shown byreference to FIG. 4. I

The activity plots of these Catalysts K and Q, and other comparativedata, thus clearly demonstrate the critical nature of maximizing poresizes in the 30 to 80 A range, and minimizing pore sizes ranging greaterthan 100 A.

EXAMPLE 9 To illustrate the use of the catalyst of this invention with ahydrocarbon residuum feed other than petroleum residua, thefollowingdata were obtained.

A feedstock was prepared by forming'a slurry from two parts ofhydrogenated creosote oil and one part Illinois No. 6 coal and passingthe slurry through a liquefaction reaction at about 675F., 350 psig, lV/V/Hr. and a hydrogen treat rate of about 0.5 wt. percent on coal. Theliquified product was centrifuged twice at 350F. to separate the bulk ofthe solids. The centrifuge overflow was used in these studies.Inspections of the feedstock are given below:

Wt. Ash 0.1

Wt. Carbon 89.5

Wt. Hydrogen 7.17

Wt. 700F. 36.0

Wt. Nitrogen 0.68

Wt. Oxygen 2.29

Specific Gravity 1.0934

The feedstock was contacted in a series of runs with Catalyst R, acatalyst of i the present invention, and other commercially useddesulfurization catalysts, S, T, and U, not of this invention. Thesecatalysts, characertized below, and used at the process conditionsdefined in Table X below, removed both nitrogen and sulfur, but CatalystR was generally superior to the others in such capacity.

TABLE X Catalyst Surface Area R 33 siduum'feed is one in which 30 100percent of th T Ni Moly on Alumina 173 54;" pills U Ni-W on FaujasiteMs" pills Conditions: l.1 W/HrJW, 700F., 2000 psig, 5000 Cu.Ft./Bbl.

Results:

Catalyst R S T U* Day 1 Conv. 41 36 42 23 Denitrogenation, Wt.

Desulfurization, 67 60 64 42 Wt. TIR for 0 L7 L0 Denitrogenation, F./Day

TIR for 0 0.55 3.0 Desulfurization, F./Day

3000 psig 'It is well known that hydrodesulfurizjtion of residua can beimproved by subjecting the feed to such pretreating steps asdeasphalting, dilution, metals removal, etc.; however, usually the costof the multistep processes cannot be justified. The process of thisinvention provides adequate sulfur removal without any other majortreating steps unless the feed has a very high metals content.

The catalysts of this invention are sufficiently active so thathydrodesulfurization reaction pressures in the range of 200 to 2,500psig are satisfactory, depending upon feedstock. Prior art processesrequire pressures of 2,500 to 3,000 psig. and a high treat gas recyclebecause of the low activity of the catalyst. Furthermore, they require25 percent more investment and higher operating costs to achieve thesame throughput. With respect to temperature, hydrodesulfurization above825F. is not practical because of excessive gas make and hydrogenconsumption. The process of the invention operates well at lowertemperatures. Conversion to light ends, gasoline and other light stocksis less than about 15 wt. percent based on the feedstock.

Having described the invention, what is claimed is:

1. A process for the hydrodesulfurization of a petro- I leum residuumcomprising contacting said residuum with a catalyst at a temperatureranging from 650 up to about 800F., a pressure of from 500 to 2,500 psigand hydrogen at a rate of 1,000 up to 5,000 standard cubic feet perbarrel (SCF/B), at a space velocity of from 0.05 to about 5.0 V/V/Hr.,said catalyst comprising the oxide or sulfide of a Group VlB metal andthe oxide or sulfide of a Group VIII metal deposited upon a supportmaterial comprising a silica-stabilized alumina containing 1-6 weightpercent of silica, said catalyst having a surface area of at least 150Mlg. and more than 50 percent of the surface area being in pores havingdiameters ranging from 30 to A.

2. The process of claim 1 wherein the petroleum refeed boils above 900F.

3. The process of claim 1 wherein the silica content of thealumina-silica composition ranges from about 1.5 5 weight percent.

4. The process of claim 1 wherein the Group VIB oxide or sulfide isselected from the group consisting of molybdenum oxide, molybdenumsulfide, tungsten oxide, tungsten sulfide, and mixtures thereof, and theGroup VIII oxide or sulfide is selected from the group consisting ofnickel oxide, cobalt oxide, nickel sulfide, cobalt sulfide, and mixturesthereof.

5. The process of claim 4 wherein the oxide or sulfide of the Group VIBmetal and Group VIII metal comprises a mixture selected from the groupconsisting. of nickel oxide with molybdenum oxide and cobalt oxide withmolybdenum oxide. I

6. A process for the hydrodesulfurization of a hydrocarbon residuum feedcomprising contacting said residuum with a catalyst at a temperatureranging from 500F. to about 825F., a pressure of from 200 to about 2,500psig and hydrogen at a rate of 300 to about 10,000 standard cubic feetper barrel (SCF/B), at a space velocity of from 0.01 to about 5.0V/V/Hr., said catalyst comprising the oxide or sulfide of a Group VlBmetal and the oxide or sulfide of a Group VIII metal deposited upon asupport material comprising a silicastabilized alumina containing 0.5-6weight percent of silica, said catalyst having at least 180 M /g. ofsurface area in pores with diameters ranging from 30 to 80 A, and lessthan 0.25 cc./g. of the pore volume in pores having a diameter greaterthan 100 A.

7. The process of claim 6 wherein the hydrocarbon residuum feed is onein which 30 100 percent of the feed boils above 900F.

8. The process of claim 6 wherein the conditions of operation are asfollows:

Temperature, F 650-800 Pressure, Psig 500-1,800

Space Velocity, V/V/Hr. 0.1-2.0

Hydrogen Rate, SCF/Bbl 1,000-7,500

9. The process of claim 6 wherein the Group VlB oxide or sulfide isselected from the group consisting of molybdenum oxide, molybdenumsulfide, tungsten oxide, tungsten sulfide, and mixtures thereof, and theGroup VIII oxide or sulfide is selected from the group consisting ofnickel oxide, cobalt oxide, nickel sulfide, cobalt sulfide, and mixturesthereof.

10. The process of claim 9 wherein the oxide or sulfide of the Group VIBmetal and Group VIII metal comprises a mixture selected from the groupconsising of nickel oxide with molybdenum oxide and cobalt oxide withmolybdenum oxide.

11. The process of claim 9 wherein the concentrations of the catalyticmetals, expressed as the oxide, is as follows:

Nickel or Cobalt l 15 wt.

Tungsten or Molybdenum 5 25 wt.

12. The process of claim 11 wherein the concentration of nickel orcobalt and tungsten or molybdenum ranges 2 10 and 10 20 weight percent,respectively.

13. The process of claim 6 wherein the silica ranges from 1 5 weightpercent.

2. The process of claim 1 wherein the petroleum residuum feed is one inwhich 30 - 100 percent of the feed boils above 900*F.
 3. The process ofclaim 1 wherein the silica content of the alumina-silica compositionranges from about 1.5 - 5 weight percent.
 4. The process of claim 1wherein the Group VIB oxide or sulfide is selected from the groupconsisting of molybdenum oxide, molybdenum sulfide, tungsten oxide,tungsten sulfide, and mixtures thereof, and the Group VIII oxide orsulfide is selected from the group consisting of nickel oxide, cobaltoxide, nickel sulfide, cobalt sulfide, and mixtures thereof.
 5. Theprocess of claim 4 wherein the oxide or sulfide of the Group VIB metaland Group VIII metal comprises a mixture selected from the groupconsisting of nickel oxide with molybdenum oxide and cobalt oxide withmolybdenum oxide.
 6. A process for the hydrodesulfurization of ahydrocarbon residuum feed comprising contacting said residuum with acatalyst at a temperature ranging from 500*F. to about 825*F., apressure of from 200 to about 2,500 psig and hydrogen at a rate of 300to about 10,000 standard cubic feet per barrel (SCF/B), at a spacevelocity of from 0.01 to about 5.0 V/V/Hr., said catalyst comprising theoxide or sulfide of a Group VIB metal and the oxide or sulfide of aGroup VIII metal deposited upon a support material comprising asilica-stabilized alumina containing 0.5-6 weight percent of silica,said catalyst having at least 180 M2/g. of surface area in pores withdiameters ranging from 30 to 80 A, and less than 0.25 cc./g. of the porevolume in pores having a diameter greater than 100 A.
 7. The process ofclaim 6 wherein the hydrocarbon residuum feed is one in which 30 - 100percent of the feed boils above 900*F.
 8. The process of claim 6 whereinthe conditions of operation are as follows: Temperature, *F - 650-800Pressure, Psig - 500-1,800 Space Velocity, V/V/Hr. - 0.1-2.0 HydrogenRate, SCF/Bb1 - 1,000-7,500
 9. The process of claim 6 wherein the GroupVIB oxide or sulfide is selected from the group consisting of molybdenumoxide, molybdenum sulfide, tungsten oxide, tungsten sulfide, andmixtures thereof, and the Group VIII oxide or sulfide is selected fromthe group consisting of nickel oxide, cobalt oxide, nickel sulfide,cobalt sulfide, and mixtures thereof.
 10. The process of claim 9 whereinthe oxide or sulfide of the Group VIB metal and Group VIII metalcomprises a mixture selected from the group consising of nickel oxidewith molybdenum oxide and cobalt oxide with molybdenum oxide.
 11. Theprocess of claim 9 wherein the concentrations of the catalytic metals,expressed as the oxide, is as follows: Nickel or Cobalt - 1 - 15 wt. %Tungsten or Molybdenum - 5 - 25 wt. %
 12. The process of claim 11wherein the concentration of nickel or cobalt and tungsten or molybdenumranges 2 - 10 and 10 - 20 weight percent, respectively.
 13. The processof claim 6 wherein the silica ranges from 1 - 5 weight percent.